Solenoid valves are used as control element in fluidic systems. The solenoid valve operates when a solenoid coil is energised by electricity. When the solenoid coil is energised, a magnetic field is created causing a plunger to linearly move, resulting in opening or closing of the valve.
Solenoid valves generally have a Normally Open (NO) and a Normally Closed (NC) position. In the Normally Closed (NC) position, the valve remains close while the solenoid coil is de-energised. When the solenoid coil is energised, the valve opens and fluid flows through the valve. When the valve is close, there is a prescribed fluidic pressure at an inlet side. There are industrial situations when there is a sudden rise in the fluidic pressure from an inlet side of the valve, above a pre-defined limit. If unchecked, there is a possibility of the valve or any element of the associated system getting damaged.
In an event of failure in electric supply to the solenoid coil or a solenoid coil open circuiting or short circuiting, the coil may stop functioning thus closing the valve and interrupting the fluid flow through the valve. This may also develop a high pressure at the inlet side of the valve.
The conventional method to solve such problem is to deploy a separate valve called as a pressure relief valve which is a safety valve to control the pressure in a system. Addition of separate valve increases the overall cost and maintenance of the system and reduces system's reliability. Without a pressure relief valve, the fluidic pressure can continue to grow until another component fails and pressure is released.
U.S. Pat. Nos. 5,992,450, 4,305,566, 3,903,919, 5,467,797 and 3,818,927 disclose the pressure relief operation when there is electric supply and do not address the issue of excessive pressure release when there is sudden rise in the fluidic pressure in absence of electrical supply to the solenoid valve.
Therefore, there is a need for a construction that overcomes the above mentioned loop holes.